The research which we now propose to carry out covers a synthetic area of natural products chemistry. The proposal includes: (1) the total synthesis of polyether antibiotics, salinomycin and ionomycin, (2) the total synthesis of rifamycins, (3) studies on the mechanisms of action of saxitoxin and tetrodotoxin, and (4) the total synthesis of gephyrotoxin. We believe these proposed studies of natural products will very effectively extend the scope of organic chemistry.